Well, you'd be completely flabbergasted about some people's views on the correlation between sales and the actual continuation of works like anime and manga. Suffice it to say that some even go so far as state that direct sales figures are an
illusion and hold no meaning over such decisions by the companies.
All very esoteric to me, as I've always believed that sales of the actual product + merchandise are what keep these companies churning out more stuff, but hey... What do I know?
As for actually buying stuff... I'm kinda compulsive to a point. Ever since buying a PS3, I haven't purchased a single DVD - other than the continuation of some anime series being released locally, simply to "complete the sets" - and I bought a good volume of Blu-Rays... Surprise, surprise, lots of anime. But I only buy stuff I can understand (and I can understand a good deal of portuguese, spanish, english, italian and french), so japanese-only stuff is difficult. Nonetheless, I do have some japanese imports, like
Princess Mononoke on DVD (which has portuguese dub and sub tracks) and some music shows/collections (stuff like May'n and some Megumi Hayashibara). TV shows and OVA's/movies, however, are a big no-no - I enjoy understanding what everyone's shouting about.